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Wu F, Yuan C, Ruan C, Zheng M, Liu L, Wang G, Chen G. Coagulation promotes the spread of antibiotic resistance genes in secondary effluents. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 355:124245. [PMID: 38810683 DOI: 10.1016/j.envpol.2024.124245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 05/04/2024] [Accepted: 05/26/2024] [Indexed: 05/31/2024]
Abstract
Wastewater treatment plants (WWTPs) are biological hotspots receiving the residual antibiotics and antibiotic resistant bacteria/genes (ARB/ARGs) that greatly influence the spread of antibiotic resistance in the environment. A common method used in WWTPs for the purification of secondary effluent is coagulation. Notwithstanding the increasing health concern of antibiotic resistance in WWTPs, the impact of coagulation on the emergence and spread of antibiotic resistance remains unclear. To shed light on this, our study investigated the behavior of four representative ARB types (tetracycline, sulfamethoxazole, clindamycin, and ciprofloxacin resistance) during the coagulation process in a model wastewater treatment plant. Our search showed a significant reduction in the presence of ARBs after either PAC or FeCl3 coagulation, with removal efficiencies of 95% and 90%, respectively. However, after 4 days of storage, ARB levels in the coagulated effluent increased by 6-138 times higher than the original secondary effluent. It suggests a potential resurgence and spread of antibiotic resistance after coagulation. Detailed studies suggest that coagulants, particularly PAC, may facilitate the transfer of ARGs among different bacterial species by the enhanced cell-cell contact during coagulation-induced bacterial aggregation. This transfer is further enhanced by the factors such as auxiliary mixing, longer incubation time and ideal operating temperatures. In addition, both PAC and FeCl3 affected gene expression associated with bacterial conjugation, leading to an increase in conjugation efficiency. In conclusion, while coagulation serves as a purification method, it might inadvertently boost the spread of ARGs during tertiary wastewater treatment. This underscores the importance of implementing subsequent measures to mitigate this effect. Our findings provide a deeper understanding of the challenges posed by bacterial antibiotic resistance in wastewater and pave the way for devising more effective ARB and ARG management strategies.
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Affiliation(s)
- Fazhu Wu
- Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Chao Yuan
- Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Chujin Ruan
- Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China; Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, 8600, Switzerland
| | - Mengqi Zheng
- Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Li Liu
- Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Gang Wang
- Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China
| | - Guowei Chen
- Department of Civil Engineering, Hefei University of Technology, Hefei, 230009, China.
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Ruan C, Borer B, Ramoneda J, Wang G, Johnson DR. Evaporation-induced hydrodynamics control plasmid transfer during surface-associated microbial growth. NPJ Biofilms Microbiomes 2023; 9:58. [PMID: 37608025 PMCID: PMC10444754 DOI: 10.1038/s41522-023-00428-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 08/15/2023] [Indexed: 08/24/2023] Open
Abstract
Droplet evaporation is a general process in unsaturated environments that results in micro-scale hydrodynamic flows which in turn determine the spatial distributions of microbial cells across surfaces. These spatial distributions can have significant effects on the development and functioning of surface-associated microbial communities, with consequences for important processes such as the spread of plasmids. Here, we experimentally quantified how evaporation-induced hydrodynamic processes modulate the initial deposition patterns of microbial cells (via the coffee ring effect and Marangoni convection) and how these patterns control the spread of an antibiotic resistance-encoding plasmid during surface-associated growth. We found that plasmid spread is a function of the initial density of cells deposited along the droplet periphery, which is a manifestation of the coffee ring effect. Using an individual-based model, we systematically linked how the different initial cell deposition patterns caused by the relative strengths of the coffee ring effect and Marangoni convection determine the extent of plasmid transfer during surface-associated growth. Our study demonstrates that evaporation-induced hydrodynamic processes that are common in nature can alter crucial ecological properties of surface-associated microbial communities and control the proliferation of plasmids, with consequences on the spread of antibiotic resistance and other plasmid-encoded traits.
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Affiliation(s)
- Chujin Ruan
- College of Land Science and Technology, China Agricultural University, Beijing, China
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
| | - Benedict Borer
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Josep Ramoneda
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
| | - Gang Wang
- College of Land Science and Technology, China Agricultural University, Beijing, China.
- National Black Soil & Agriculture Research, China Agricultural University, Beijing, China.
| | - David R Johnson
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland.
- Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.
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Ruan C, Ramoneda J, Gogia G, Wang G, Johnson DR. Fungal hyphae regulate bacterial diversity and plasmid-mediated functional novelty during range expansion. Curr Biol 2022; 32:5285-5294.e4. [PMID: 36455559 DOI: 10.1016/j.cub.2022.11.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 09/20/2022] [Accepted: 11/03/2022] [Indexed: 12/05/2022]
Abstract
The amount of bacterial diversity present on many surfaces is enormous; however, how these levels of diversity persist in the face of the purifying processes that occur as bacterial communities expand across space (referred to here as range expansion) remains enigmatic. We shed light on this apparent paradox by providing mechanistic evidence for a strong role of fungal hyphae-mediated dispersal on regulating bacterial diversity during range expansion. Using pairs of fluorescently labeled bacterial strains and a hyphae-forming fungal strain that expand together across a nutrient-amended surface, we show that a hyphal network increases the spatial intermixing and extent of range expansion of the bacterial strains. This is true regardless of the type of interaction (competition or resource cross-feeding) imposed between the bacterial strains. We further show that the underlying cause is that flagellar motility drives bacterial dispersal along the hyphal network, which counteracts the purifying effects of ecological drift at the expansion frontier. We finally demonstrate that hyphae-mediated spatial intermixing increases the conjugation-mediated spread of plasmid-encoded antibiotic resistance. In conclusion, fungal hyphae are important regulators of bacterial diversity and promote plasmid-mediated functional novelty during range expansion in an interaction-independent manner.
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Affiliation(s)
- Chujin Ruan
- College of Land Science and Technology, China Agricultural University, 100193 Beijing, China; Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland
| | - Josep Ramoneda
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
| | - Guram Gogia
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland; Department of Environmental Systems Science, Swiss Federal Institute of Technology, 8092 Zürich, Switzerland
| | - Gang Wang
- College of Land Science and Technology, China Agricultural University, 100193 Beijing, China; National Black Soil & Agriculture Research, China Agricultural University, 100193 Beijing, China.
| | - David R Johnson
- Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland; Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.
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Orevi T, Sørensen SJ, Kashtan N. Droplet size and surface hydrophobicity enhance bacterial plasmid transfer rates in microscopic surface wetness. ISME COMMUNICATIONS 2022; 2:72. [PMID: 37938682 PMCID: PMC9723546 DOI: 10.1038/s43705-022-00159-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 07/25/2022] [Accepted: 08/02/2022] [Indexed: 11/09/2023]
Abstract
Conjugal plasmids constitute a major engine for horizontal gene transfer in bacteria, and are key drivers of the spread of antibiotic resistance, virulence, and metabolic functions. Bacteria in terrestrial habitats often inhabit surfaces that are not constantly water-saturated, where microscopic surface wetness (MSW), comprised of thin liquid films and microdroplets, permanently or intermittently occurs. How physical properties of microdroplets, and of the surfaces they reside on, affect plasmid transfer rates is not well understood. Here, building on microscopy-based microdroplet experiments, we examined the relation between droplet properties (size and spread) and plasmid transfer rates at single-cell and individual droplet resolution, using Pseudomonas putida as a model species. We show that transfer rates increase with droplet size, due to higher densities of cells on the surface in larger droplets, resulting from lower ratio between the area of the liquid-solid interface and droplet volumes. We further show that surface hydrophobicity promotes transfer rates via the same mechanism. Our results provide new insights into how physical properties of surfaces and MSW affect plasmid transfer rates, and more generally, microbial interactions mediated by cell-to-cell contact, with important implications for our understanding of the ecology and evolution of bacteria in unsaturated environments.
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Affiliation(s)
- Tomer Orevi
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University, Rehovot, 76100, Israel
| | - Søren J Sørensen
- Department of Biology, University of Copenhagen, DK 2100, Copenhagen, Denmark
| | - Nadav Kashtan
- Department of Plant Pathology and Microbiology, Institute of Environmental Sciences, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University, Rehovot, 76100, Israel.
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